1. Field of the Invention
The invention herein relates to the production of volatile metals, especially copper. More particularly it relates to production of metals in a volatile state suitable for vapor deposition of such metals.
2. Description of the Prior Art
Vapor deposition of metals as coatings on substrates, including coatings which can form active metal layers of semiconductors, has been known for some time. Aluminum has been the metal most commonly used in vapor deposition for formation of semiconductor materials. Recently, however, reports have appeared in the literature describing formation of semiconductor interconnects from deposited copper.
Because vapor deposition is a convenient and effective way of depositing a pure metal on a substrate, numerous patents have been issued describing methods of volatilizing metals, including copper, for vapor deposition. In general these processes have required, as starting materials, various organic or inorganic compounds or complexes of the metal to be deposited. Other processes for volatilizing metal, either from a metal source or from a metal compound or complex source, have required the maintenance of a vacuum to achieve the volatilization. All of these processes have been complicated and expensive. In addition, where the various compounds or complexes of the metal have been used as starting materials, there is a residue of the volatilization reaction to be adequately disposed of.
It would therefore be of value to have a process which would permit the production of volatilized metal in a manner which does not require the use of compounds or complexes which are difficult to react and/or leave undesirable residues (as in chemical vapor deposition), or which does not require the production and maintenance of a high vacuum environment (as in physical vapor deposition ["PVD"]).